Downing Street has said Boris Johnson wants to negotiate a new Brexit deal "with the greatest energy", amid reports EU leaders have accepted the UK is going to leave without an agreement.
Brussels is said to be operating on a "working hypothesis of no-deal" after accepting the prime minister "isn't bluffing" about crashing out of the bloc.
It comes after a meeting on Monday between European Commission officials and Brexit diplomats from the 27 other EU member states.
Number 10 insisted on Monday that Brussels must "change its stance" to secure an agreement.
The prime minister wants to hold talks about a fresh deal but the EU needs to "rethink" its "current refusal" to make any changes to the withdrawal agreement, Downing Street added.
The statement comes after reports emerged about a briefing to diplomats in Brussels.
It followed a meeting between Mr Johnson's top Europe adviser David Frost and senior EU figures last week.
Mr Frost was sent to Brussels to deliver the message that the UK will be leaving on 31 October "whatever the circumstances".
A senior EU diplomat is quoted by The Daily Telegraph and The Guardian as saying a no-deal Brexit appears to be the UK government's "central scenario".
They are reported to have said: "Our working hypothesis is no-deal."
The diplomat added: "It was clear the UK does not have another plan. No intention to negotiate, which would require a plan.
"A no-deal now appears to be the UK government's central scenario."
EU officials are reported to have said there is no basis at the moment for "meaningful discussions" with the UK over Brexit.
Mr Frost reportedly sought discussions on how negotiations could be reset after the UK is expected to leave on 31 October.
He is also reported to have told officials that a technological solution to the Irish backstop was the preferred option, before admitting that "it would not be ready now for Brexit".
A Brussels source is said to have concluded after the discussion: "Even if the EU gave up the backstop there is no alternative.
"That message has now gone loud and clear to capitals, it was useful to hear it from horse's mouth.
"Reality is sinking in."
Mr Johnson has ramped up planning for a no-deal Brexit since he took power.
This is despite claiming the odds of it happening are a "million to one against".
A Downing Street spokeswoman said: "The PM wants to meet EU leaders and negotiate a new deal - one that abolishes the anti-democratic backstop.
"We will throw ourselves into the negotiations with the greatest energy and the spirit of friendship and we hope the EU will rethink its current refusal to make any changes to the withdrawal agreement.
"The fact is the withdrawal agreement has been rejected by parliament three times and will not pass in its current form so if the EU wants a deal, it needs to change its stance.
"Until then, we will continue to prepare to leave the EU on 31 October."
Labour leader Jeremy Corbyn had previously said he would call for a vote of no confidence in the government this autumn in an attempt to stop a no-deal Brexit.
Mr Corbyn said the party would do this "when we can win it" but added it would be at an "appropriate very early time".
Mr Johnson said the "last thing" he wanted to do was call a general election.
Health Secretary Matt Hancock also issued a fresh warning to rebel Tory MPs that they cannot stop Mr Johnson taking Britain out of the EU without a deal.
Mr Corbyn, speaking on a visit to Whaley Bridge in Derbyshire, said: "We will do everything to stop no deal including a no confidence vote at the appropriate very early time to do it.
"The prime minister seems to be trying to slip no-deal through, slip past parliament and slip past the British people.
"Sorry, no-deal will be really serious."
Asked whether he would be preparing to fight a general election based on Labour winning a vote of no confidence, the prime minister said: "No. The answer is no.
"The people of the UK voted in the election 2015, they had a referendum in 2016, and another election in 2017.
"They want us to deliver what they asked for - and that is for us to leave the EU. The last thing I want to do is call another election."
At an earlier briefing for political journalists at Westminster, the prime minister's spokesman repeatedly refused to be drawn on what the government would do if MPs voted against no deal, saying it was a "hypothetical" question.
The spokesman said: "The legal default, as put in place by parliament, is that we will be leaving on 31 October."
